Koenig, P.; Truong, A.; Lehman, H.; Sanchez, B.-J.; Grasis, J. A.; Sukenik, S.

Intrinsically Disordered Proteins and protein regions (IDPs) are abundant in many viral proteomes and play diverse roles in the viral infectious cycles. The adenovirus Early Protein 1A (E1A) is one such viral IDP. E1A acts as a molecular hub that regulates viral infection by mediating interactions between viral and multiple host proteins. Like other IDPs, E1A exists in a flexible ensemble of conformations. Despite a demonstrated link between ensemble structure and function in E1A, no real-time measurement of its ensemble has been performed. Here, we use live cell FRET microscopy to measure the local ensemble structure of E1A in human cells, both in healthy cells and in cells infected with adenovirus. We found specific disordered regions undergo significant changes to their ensemble in infected cells. Furthermore, infection also alters the propensity of these regions to partition between the cytoplasm and nucleus, a hallmark of E1A function during infection. Our results showcase that the structural ensembles of viral IDPs are responsive to infection, and suggest that these may play a role in regulating infection progression.